There are 3 Imposters, and you must catch them. Watch the security cameras and look for anyone committing a kill. When you see a murder, click the killer before he can escape. If they are an Imposter, they vanish. You lose if you click 3 innocent people or if the Imposters eliminate the entire group. You win if you catch all 3 imposters. Good luck!
Update log: v1.1 - Changes turtorial to make it less confusing.